The Conservative party's prized trust on managing the economy is beginning to crumble, according to a Guardian/ICM poll, which shows that Ed Miliband and Ed Balls are now within touching distance of David Cameron and George Osborne on the all-important question of financial competence.

The regular Guardian/ICM survey finds that Labour retains a solid overall lead on voting intention, although this is somewhat smaller than last month. After Miliband's well-reviewed "One Nation" speech at his party's conference, Labour remains on 41%, a score which it has not improved in the series since 2003, when Iain Duncan Smith was Conservative leader. That puts them eight points clear of the Conservatives, who are up by two on 33%. There is no change for the Liberal Democrats, who remain stuck on 14%, while the assorted minor parties' support adds up to 12%, down one on last month.

The Conservative bounceback suggests that their 31% score last month, worse than anything previously seen under the Cameron leadership, could be a blip. That is good news for the prime minister after a turbulent week at Westminster, which ended with the resignation of the chief whip Andrew Mitchell on Friday. But he is losing ground on the crucial economic terrain.

When voters are asked to put their party preferences aside and consider which team is better placed to manage the economy properly, 31% prefer Cameron and Osborne, as against 27% for Miliband and Balls. The Conservative team thus holds a four-point edge, though this advantage is the lowest on record on a question which ICM has asked repeatedly during the last year. The Tories' advantage was 21 points last Christmas, and has steadily dwindled since, but during the months since, the gap has never been less than nine.

The survey was conducted at the end of a week in which unemployment and inflation both fell, but Cameron and Osborne's own 31% score has dropped particularly sharply – down from 40% since the question was last asked in July. The crumb of comfort for the government is that most doubters have moved into the don't know column, rather than moving over to Labour. Indeed, trust in the Miliband-Balls team is also down since July, albeit only by two points.

Before this week's feminist lobby of parliament, Labour has notched up a big 46%-32% lead among female voters. Miliband's party also enjoys solid support of 40% or more across all social classes, although it remains stuck just below this level – at 38%-39% – across the electorally important Midlands and the south.

The small print of the survey provides powerful evidence of a generation gap. Among those aged 25-34, Labour is outpolling the Tories by 59% to 18%, a crushing three to one margin. But among pensioners, who are more likely to turn out and vote, the Conservatives retain a 46%-32% lead.

Labour's eight-point lead with ICM is at the bottom end of a range of polls published over the weekend, which put the opposition's lead at everything from eight to 13 points. ICM's raw figures show a bigger 43%-32% gap, but the pollsters adjust to identify so-called "shy Tory" voters, by assuming that a proportion of those who report voting a particular way last time around but refuse to say who they will back next time will in fact revert to past form. The same adjustment boosts Lib Dem support more substantially, from 11% to 14%, which helps explains why ICM continues to rate the third party more highly than other pollsters, who often put them on 10% or less. Experience has demonstrated that this sort of adjustment in favour of parties who have fallen out of fashion is a valuable way of ironing out wilder political vicissitudes to give a more robust prediction. Support for the individual minor parties was as follows: Ukip 5%, SNP 3%, Greens 2%.

ICM Research interviewed a random sample of 1,000 adults aged 18+ by telephone on 19-22 October 2012. Interviews were conducted across the country and the results have been weighted to the profile of all adults. ICM is a member of the British Polling Council and abides by its rules.